Image forming method and transfer recording medium therefor

ABSTRACT

A transfer recording medium comprising a transfer recording layer is provided. The transfer recording layer causes an irreversible change in transfer characteristic when provided with plural kinds of energies such as heat, light and pressure energies. Such plural energies are applied to the transfer recording layer with at least one energy applied imagewise to provided a transferable portion or latent image portion in the transfer recording layer. The transferable portion is then transferred to a medium such as plain paper. The provision of plural kinds of energies aids in realization of high quality multi-color transfer image in a compact apparatus through functional separation of image formation and transfer operations. Further, even a multi-color image can be obtained through a single transfer step.

This is a division of application Ser. No. 869,689filed June 2, 1986.

FIELD OF THE INVENTION AND RELATED ART

The present invention relates to an image forming method, a transferrecording medium and an image forming apparatus applicable for printers,copying machines, and facsimile machines.

In recent years, accompanying the rapid progress of the informationindustry, various information processing systems have been developed,and various recording methods and apparatus have been developedcorresponding to respective information processing systems. As arecording method among such recording methods, the heat-sensitive orthermal transfer recording method has advantages since the apparatusemployed is light in weight, compact, free of noise, excellent inoperability and adapted to easy maintenance. Accordingly it has beenrecently widely used. According to this method, plain paper can be usedas a medium to be transfer-printed or as a recording medium.

However, the heat-sensitive transfer recording method of the prior artis not free from drawbacks. That is, according to the heat-sensitivetransfer recording method of the prior art, the transfer recordingperformance, namely the printed letter quality, is remarkably influencedby the surface smoothness of the recording medium, and therefore whilegood printing can be effected on a recording medium having highsmoothness, the printed letter quality will be markedly lowered in thecase of a paper with low smoothness. However even paper which is themost typical recording medium present problems paper with highsmoothness is rather unusual. Ordinary paper exhibits surface unevenessto various extents because they are formed through entanglements offibers As a result, according to the conventional heat-sensitivetransfer recording method, the resulting printed image may not be sharpat the edge portion or a part of the image may be missing which lowersthe printed letter plurality.

Further, in the conventional heat-sensitive transfer recording method,while the transfer of an ink layer to the medium to be transfer printedis caused by only the heat supplied from a thermal head, it is difficulteven from a theoretical point of view to increase the heat supply fromthe thermal head. That is a problem because it is required to cool thethermal head to a prescribed temperature in a limited short time and itis also necessary to prevent occurrence of thermal crosstalk betweenheat-generation segments or elements constituting the thermal head face.For this reason, high speed recording has been difficult to realizeaccording to the conventional heat-sensitive transfer recording method.

Further, as heat conduction has a slow response speed compared withelectricity or light, it has been generally difficult to control a heatsufficient to be capable of reproduce a medium tone by the conventionalrecording system using a transfer medium, and also it has beenimpossible to effect a medium tone recording as the conventionalheat-sensitive transfer ink layer lacks a transfer function forgradational representation.

Further, in the conventional heat-sensitive transfer recording method,it has been only possible to obtain one image through one transferoperation, and accordingly, it has been necessary to repeat severaltimes the transfer step to superpose colors in order to obtain amulti-color image. Since it is very difficult to exactly superposeimages of different colors it has been difficult to obtain an image freeof color deviation or aberration. Particularly, when one picture elementis involved superposition of colors has not been effected in such a onepicture element, and consequently, a multi-color image has beenconstituted by assembly or gathering of picture elements involving colordeviation in the conventional heat-sensitive transfer recording method.For this reason, it has been impossible to obtain a clear multi-colorimage according to the conventional heat-sensitive transfer recordingmethod.

Further, when it is devised to obtain a multi-color image by theconventional heat-sensitive transfer recording method, there have beenattendant difficulties, of plural thermal heads or complex movementreproduce of direction involving and stopping of media to be printedwhich require a large and complex apparatus or a decrease in recordingspeed.

This has been proposed a transfer imaging method for producing amulticolor image by using a color precursor chromagenic material and adeveloper (U.S. Pat. No. 4,399,209). More specifically, in this method,an imaging sheet comprising a substrate and a coating thereon comprisinga chromagenic material and a radiation curable composition encapsulatedin rupturable capsules, is provided; the coating is subjected toimagewise exposure with actinic radiation to cure the radiation curablecomposition and form a latent image and the latent image is superposedonto a developer sheet to form a visible image or the developer sheet.In such a known method, only light energy is used for forming a latentimage on a transfer recording method (image sheet), so that a recordingmedium highly sensitive to light or a light flux of a high energy isrequired in order to obtain a clear image at a high speed. A highsensitivity recording medium generally has poor storage stability and istherefore inappropriate for easy handling. Further, it is difficult toobtain the high energy required for curing a radiation-curablecomposition at a high speed with a single kind of energy, particularly alight energy. Accordingly, a large apparatus has been generallyrequired.

SUMMARY OF THE INVENTION

It is therefore a principal object of the present invention to providean image forming method which has solved the above mentioned problemsaccompanying the conventional heat-sensitive transfer recording method.

A specific object of the present invention is to provide an imageforming method by which a high-quality transfer image can be formed onplain paper which has a low surface smoothness and is a most popularrecording medium or medium to be transfer-printed.

A further object of the present invention is to provide an image formingmethod which affords a high speed recording and a medium tone recording.

A still further object of the present invention is to provide an imageforming method which affords a clear multi-color transfer image withoutrequiring a complicated movement of a medium to be transfer printed.

Another object of the present invention is to provide a transferrecording medium and an image forming apparatus adapted for use in theabove mentioned image forming method.

According to a principal aspect of the present invention, there isprovided an image forming method, comprising providing a transferrecording medium comprising a transfer recording layer, said transferrecording layer being capable of causing an irreversible change intransfer characteristic thereof when provide with plural kinds ofenergies; imparting the plural kinds of energies to the transferrecording layer under such a condition that at least one of the pluralkinds of energies is imparted imagewise, i.e., corresponds to arecording information signal, thereby to form a transferable portion inthe transfer recording layer; and transferring the transferable portionof the transfer recording layer to a transfer-receiving medium or mediumto be transfer-printed, thereby to leave an image corresponding to thetransferable portion on the transfer-receiving medium or medium to betransfer-printed.

The term "irreversible change in transfer characteristic" used hereinmeans that the change in transfer characteristic caused by provision ofthe plural kinds of energies lasts even after the removal of theenergies and is retained semi-permanently or at least until thesubsequent transfer step. The term "transferable portion" or "latentimage (portion)" used herein means a portion of the transfer recordinglayer provided by local change in the transfer characteristic. Thetransferable portion or latent image (portion) is generally not clearlyvisible but can be visible.

These and other objects, features and advantages of the presentinvention will become more apparent upon a consideration of thefollowing description of the preferred embodiments of the presentinvention taken in conjunction with the accompanying drawings, whereinlike parts are denoted by like reference numerals.

"Parts" or "%" used hereinafter with reference to a composition are byweight unless otherwise noted specifically.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A-1D show changes of several parameters with elapse of timeinvolved in a latent image forming step according to the presentinvention;

FIG. 2A-2D are schematic partial sectional views showing a relationshipbetween a transfer recording medium and a thermal head involved in amulti-color transfer recording mode according to the present invention;

FIGS. 3-8, 12 and 14 are respectively a schematic side view showing anexample of a system arrangement for practicing the image forming methodaccording to the present invention;

FIGS. 9 and 11 are respectively a timing chart for driving the energysources used in an embodiment for practicing the image forming methodaccording to the present invention;

FIGS. 10 and 13 respectively show spectral characteristic curves oflight fluxes for illuminating a transfer recording medium in an exampleof the image forming method; and

FIG. 15 is an enlarged partial plan view of a liquid crystal shutterarray used in an embodiment shown in FIG. 14.

DETAILED DESCRIPTION OF THE INVENTION

In the image forming method according to the present invention, a latentimage to be transferred may be formed by changing a physical propertycontrolling a transfer characteristic. The physical property controllinga transfer characteristic may be determined depending on a particulartype of transfer recording medium used. For example, with respect to atransfer recording medium used in a transfer mode wherein transfer of animage is effected through heat fusion of the image, the physicalproperty may be a melting temperature, a softening temperature, a glasstransition temperature, etc. With respect to a transfer recording mediumused in a transfer mode wherein transfer of image is effected by makingan image to be transferred viscous or penetrable into a medium to betransfer printed, the physical property may be a viscosity at therelevant temperature Further, plural kinds of energy used for providingtransfer images may also be determined depending on the type of transferrecording medium used, inclusive of light, electron beam, heat,pressure, etc., which may be appropriately combined.

For comprehension of the image forming method according to the presentinvention, an example of using a transfer recording medium for which alatent image is formed by light and heat energies is explained withreference to FIGS. 1A to 1D, wherein the abscissas are indicated on acommon scale of time. The transfer recording layer contains a reactioninitiator, a polymerizing component, etc., which will be explainedhereinafter. FIG. 1A shows a surface temperature change of a heatingelement when a heating means such as a thermal head is energized forheat generation for a period of 0 - t₃ and subjected to temperaturedecrease thereafter A transfer recording medium contacting the heatingmeans under pressure causes a temperature change as shown in FIG. 1Bcorresponding to the temperature change of the heating means. Morespecifically, it starts to cause a temperature rise after a time delayof t₁ and similarly reaches the maximum temperature at time t₄ aftertime t₃, then followed by temperature decrease The transfer recordinglayer has a softening temperature Ts and abruptly softens to decreaseits viscosity in a temperature region above Ts. The change in viscosityis shown by a curve A in FIG. 1C. Thus, after the temperature reaches Tsat time t₂ and until it reaches the maximum temperature at time t₄, theviscosity continually decreases, while the viscosity again increasesthereafter along with temperature decrease to show an abrupt increase inviscosity until time t₆ when the temperature decreases to Ts. In thiscase, the transfer recording layer has not been basically subjected toany material change and shows a decrease in viscosity in the manner asdescribed above when it is heated above Ts in a subsequent transferstep.

Accordingly, if the transfer recording layer is caused to contact amedium to be transfer printed under pressure and subjected to heatingrequired for transfer, e.g., to a temperature above Ts, the transfer.recording layer is transferred in the same transfer mechanism asinvolved in the conventional heat-sensitive transfer recording. In thisinvention, however, when the transfer recording layer is illuminated orexposed to light from t₂ in parallel with heating as shown in FIG. 1D,and the temperature is sufficiently increased, the transfer recordinglayer softens and the reaction initiator, is actuated to provide a largereaction velocity and the polymerizing component rapidly causes curingor hardening, sometimes involving crosslinking.

In this way, if heating and illumination are simultaneously carried out,the transfer recording layer shows a viscosity change as represented bya curve B in FIG. 1C. Then, along with further progress of curing, thesoftening temperature is raised from Ts to Ts' at time t₂ when thecuring is completed. Corresponding to this, the transfer recording layeris caused to have a different transfer initiation temperature, i.e., atemperature at which it starts to be transferred, from Ta to Ta'. Thechange in softening temperature as described above of the transferrecording layer is illustrated in FIG. 1D. As a result, the transferrecording layer has a portion having a transfer initiation temperatureTa' and also a portion retaining a transfer initiation temperature Tawhich behave differently in a subsequent transfer step. Now, when thetransfer recording layer is heated to a temperature Tr satisfyingTa<Tr<Ta', the portion having a transfer initiation temperature Tapreferentially causes an abrupt decrease in viscosity to be selectivelytransferred to a medium to be transfer-printed. In this instance, Ta' -Ta (or Ts' - Ts) should preferably be about 20° C. or more while itsomewhat depends on temperature stabilization accuracy during thetransfer step. In this way, a latent image may be formed by controllingheating or non-heating in combination with simultaneous illumination,corresponding to an image signal.

As will be understood from the above description, the degree ofirreversible change in transfer characteristic required for the transferrecording layer in the present invention is conveniently represented bya change in transfer initiation temperature. Herein, the transferinitiation temperature mentioned herein is a value measured by thefollowing method.

A 6 μ-thick transfer recording layer formed on a 6 μ-thick polyethyleneterephthalate (PET) film is caused to contact 0.2 mm-thick wood-freepaper as a medium to be transfer-printed having a surface smoothness(Bekk smoothness) of 50-200 seconds The resultant laminate of thetransfer recording medium and the paper is passed at a rate of 2.5mm/sec be ween a pair of rolls as follows. The first roller is a hollowcylindrical iron roller of 40 mm diameter in which a 300 W-halogen lampheater is stored and is disposed on the side of the transfer recordingmedium. The second roller disposed on the side of the paper comprises asimilar iron roller of 40 mm diameter coated with a 0.5 mm-thickfluorine rubber layer. The two rollers are operated to exert a linearpressure of 4 kg/cm. In the measurement, the surface temperature of thefirst roller is measured by a temperature sensor, e.g., a thermistor,while controlling the halogen lamp heater to provide a prescribedtemperature. At a time of 4 seconds after the laminate is passed throughthe two rollers, the transfer recording method is peeled off the papermoved horizontally at a peeling angle of about 90° and at a rate equalto the conveying speed of the rollers, so that it is observed whetherthe transfer recording layer has been transferred onto the paper. Theoperation is continued while gradually raising the surface temperatureof the first roller (at a rate of 10° C./min or less), and the minimumtemperature at which the transfer starts to occur effectively (asidentified by saturation of a transferred image density) is identifiedas the transfer initiation temperature of the transfer recording mediumor the transfer recording layer. The measurement of the transferinitiation temperature is conducted in the same manner both before andafter an imaging operation or provision of plural kinds of energies.

The irreversible change in transfer characteristic may alternatively berepresented by a change in softening temperature of the transferrecording layer. The softening temperature of the transfer recordinglayer may conveniently be determined by the thermal mechanical analysis(TMA) which is in principle a method wherein a softening temperature ofa sample is determined by subjecting the sample to a constant weightexerted by a needle and gradually heating the sample to observe how theneedle penetrates into the sample. Herein, the softening temperature isbased or a value measured in the following manner. Thus a 20 μ-thicktransfer recording layer is formed on a 1 mm-thick Al-substrate andsubjected to a pressure of 70 g/cm² exerted by 500 mg-weight through astraight needle having a tip area of 0.7 mm². The temperature is raisedat a rate of 10° C./min and the penetration behavior of the needle isobserved. The softening temperature is given by a temperature at whichthe penetration speed abruptly increases.

The degree of change in transfer initiation temperature or softeningtemperature of a transfer recording layer before and after the provisionof plural kinds of energies is preferably 20° C. or more, particularly40° C. or more.

The irreversible change in transfer characteristic of a transferrecording layer may also be represented by change in another physicalproperty such as a melting temperature, a glass transition temperature,etc., instead of the transfer initiation temperature or softeningtemperature as described above. In any case, a latent image may beformed in a transfer recording layer by utilizing an irreversible changein melting temperature, glass transition temperature, etc. As themelting temperature and glass transition temperature change with asimilar tendency as a softening temperature, the change in meltingtemperature or glass transition temperature may be similarly utilized inthe manner as described above with respect to the softening temperature.

Based on the above explanation for reference, an embodiment ofmulti-color image forming method will be explained.

FIGS. 2A-2D are schematic partial sectional views showing a relationshipbetween a transfer recording medium and a thermal head according to thepresent invention. In this embodiment, a heat energy modulated accordingto a recording signal is applied in combination with a light energyselected depending on the color of an image forming element of which thephysical property controlling a transfer characteristic is intended tobe changed. Herein, "modulation" is an operation of changing a positionto which the energy is applied corresponding to a given image signal,and "in combination" covers a case where the light energy and the heatenergy are applied simultaneously as well as a case where the lightenergy and the heat energy are applied separately.

A multi-color transfer recording medium 1 according to this embodimentcomprises a transfer recording layer 1a disposed on a base film 1b. Thetransfer recording layer 1a is formed as a layer of distributed minuteimage forming elements 31. Respective image forming elements showdifferent color tones. In the embodiment shown in FIGS. 2A-2D, forexample, each image forming element 31 contains any one colorantselected from cyan (C), magenta (M), yellow (Y) and black (K). Thecolorants to be contained in the image forming elements 31, however, arenot restricted to cyan, magenta, yellow and black, but may be colorantsof any color depending on an intended use. Each image forming element 31contains in addition to a colorant, a functional or sensitive component,of which the physical property controlling a transfer characteristicabruptly changes when light and heat energies are applied thereto. Theimage forming elements 31 may be formed on the substrate 1b togetherwith a binder or by heat-melting the above components.

The functional component in the image forming elements 31 has awavelength dependency depending on the colorant contained. Morespecifically, an image forming element 31 containing a yellow colorantcauses abrupt crosslinking to be cured when a heat flux and a light beamwith a wavelength (Y) are applied thereto. Similarly, an image formingelement 31 containing a magenta colorant, an image forming element 31containing a cyan colorant and an image forming element 31 containing ablack colorant respectively cause abrupt crosslinking to be cured when aheat and a light beam with a wavelength λ(M), heat and a light beam witha wavelength λ (C), and heat and a light beam with a wavelength λ (K),respectively, are applied thereto. A cured or hardened image formingelement 31 does not cause decrease in viscosity even when heated in asubsequent transfer step, so that it is not transferred to a medium tobe transfer-printed. The heat and light are applied corresponding to aninformation signal to be recorded.

In this embodiment of the image forming method according to the presentinvention, the transfer recording method 1 is superposed on a thermalhead 20, and light is illuminated so as to cover the entire heatgeneration region of the thermal head 20. The wavelengths of theillumination light are so selected sequentially as to react on imageforming elements to be illuminated. For example, if image formingelements 31 to be illuminated are colored in any one of cyan, magenta,yellow and black, light beams having a wavelength λ(C), λ(M), λ(Y) andλ(K), respectively, are successively irradiated.

More specifically, while the transfer recording method is illuminatedwith a light beam having a wavelength λ(Y), resistance heating elements20b, 20d, 20e and 20f, for example, of the thermal head are caused togenerate heat As a result, among the image forming elements 31containing a yellow colorant, those applied with the heat and the lightbeam with a wavelength λ(Y) are cured as shown by hatching in FIG. 2A(In FIGS. 2B, et seq., the cured elements are also indicated byhatching).

Then, as shown in FIG. 2B, while the transfer recording layer 1a isilluminated with a light beam with a wavelength λ(M), resistance heatingelements 20a, 20e and 20f are caused to generate heat, whereby among theimage forming elements containing a magenta colorant, those applied withthe heat and the light beam with a wavelength λ(M) are cured. Further,as shown in FIGS. 2C and 2D, while the light fluxes with wavelengthsλ(C) and λ(D) are provided, prescribed resistance heating elements arecaused to generate heat, whereby image forming elements applied with theheat and light are cured to finally leave a latent image formed ofnon-cured image forming elements 31. The latent image is thentransferred to a medium to be transfer-printed 10 in a subsequenttransfer step as shown in FIG. 2E.

In the transfer step, the transfer recording medium on which the latentimage has been formed is caused to contact the medium to betransfer-printed 10 through the faces and heat is applied from thetransfer recording medium side or the medium 10 side, whereby the latentimage is selectively transferred to the medium to be transfer-printed 10to form a visible image thereon. Accordingly, the heating temperature inthe transfer step is so determined in connection with the change intransfer characteristics that the latent image is selectivelytransferred. Further, in order to effectively carry out the transfer, itis also effective to apply a pressure simultaneously. The pressurizationis particularly effective when a medium to be transfer-printed having alow surface smoothness is used. Further, where the physical propertycontrolling a transfer characteristic is a viscosity at roomtemperature, the pressurization alone is sufficient to effect thetransfer.

The heating in the transfer step is suitable for producing a durablemulti-color image with a stability and an excellent storability.

In the above embodiment explained with reference to FIGS. 2A to 2D, theentire area of the thermal head 20 is illuminated with light whileresistance heating elements of the thermal head 20 are selectivelyenergized. On the contrary, while a certain area of the transferrecording medium are uniformly heated, e.g., by energizing all theresistance heating elements of the thermal head 20 shown in FIG. 20,light illumination may be effected selectively or imagewise to form asimilar multi-color image. More specifically, light energy having awavelength modulated according to a recording signal and selecteddepending on the color of an image forming element of which the physicalproperty controlling a transfer characteristic is intended to bechanged, is imparted along with heat energy.

Referring to FIG. 2A, the thermal head 20 is entirely and uniformlyenergized instead of selectively energizing resistance heating elements20b, 20d, 20e and 20f, while the transfer recording layer 1a at theportions corresponding to the resistance heating elements 20b, 20d, 20eand 20f is illuminated with a light beam having a wavelength λ(Y). Also,when a light beam having λ(M) is used, the entirety of the thermal head20 is energized and the parts corresponding to the resistance heatingelements 20a, 20e and 20f are illuminated. The illumination with lightbeams having wavelengths λ(C) and λ(K) is similarly conducted.

In the above explanation, the means for entirely and uniformly heatingthe transfer recording layer 1a has been explained to be a thermal headbut may be another uniform heating means such as a heating roller or ahot plate.

Further, in the above explanation, the image forming elementstransferred to the medium to be transfer-printed (e.g., a recordingpaper) are depicted as discrete points for convenience of explanation inFIG. 2E, but may actually be spread two-dimensionally on the medium tobe transfer-printed, so that they form respective picture elements inorder, e.g., corresponding to respective heating elements of the thermalhead in the embodiment shown in FIGS. 2A-2E.

In the above, there has been explained an embodiment wherein respectiveimage forming elements have a sensitivity to a particular spectralregion. This is not an essential requirement. If materials havingsensitivities to different temperatures are used in respective imageforming elements, they can be differentiated by applying different heatenergies even if they do not have different spectral sensitivities. Morespecifically, if image forming elements having temperature dependenciesare used, it is possible to uniformly irradiate the image formingelements with light and apply heat energies as information signalsvarying with colors of respective image forming elements.

In the above embodiment with reference to FIGS. 2A to 2E, a multi-colorimage is obtained by using a transfer recording method according to thepresent invention. However, a monocolor image may also be produced byusing a similar transfer recording method if a single colorant is usedin all the image forming elements. In this case, it is not necessary tohave the functional components correspond to respective colorants.

In the embodiment shown in FIGS. 2A-2E, the transfer recording layer 1ais formed as a coating layer of particulate image forming elements, butmay also be a uniformly melted continuous coating layer. Further, theparticulate image forming elements may also be in the form of capsuleseach comprising a core and a wall encapsulating the core In case ofcapsular image forming elements, the colorant and the functionalcomponent are generally contained in the core. In order to obtain amulti-color image, particulate or capsular particulate image formingelements may preferably be used. Such image forming elements maypreferably be distributed at a rate of 25% to the closest packing statein terms of the projection area to the substrate. In a case where thetransfer recording layer is formed of capsular image forming elements,the walls of the image forming elements are ruptured in the transferstep to mainly transfer the core material onto a medium to betransferred to form a image thereon. Accordingly, the heatingtemperature in the transfer step is so determined in connection with thechange in transfer characteristic that the latent image is selectivelytransferred.

The transfer recording medium used in the present invention may be anyone having a transfer recording layer capable of causing an irreversiblechange in transfer characteristic when provided with plural kinds ofenergies Such an irreversible change in transfer characteristic may becaused through changes in physical properties such as meltingtemperature, softening temperature, glass transition temperature, andviscosity.

The image forming elements constituting, a transfer recording layercontains a functional component and a colorant The functional componentmay preferably be a substance which can initiate a reaction leading tothe physical property change or can abruptly change the velocity of sucha reaction when provided or irradiated with plural energies such aslight and heat. The functional component may be defined as a componentprincipally responsible for the above mentioned irreversible change intransfer characteristic of the transfer recording layer and may includea polymerizable component or depolymerizing component, and an optionallyused initiator and sensitizer, as will be described hereinafter.

A typical example of such a functional component may be a polymerizingcomponent such as a monomer, oligomer or polymer.

Specific examples of the oligomer or polymer include those compoundshaving a reactive group at a terminal or in a side chain such aspolyvinyl cinnamate, p-methoxycinnamic acid-succinic acid half estercopolymer, polyvinylstyrylpyridinium, polymethyl vinyl ketone,polyethylene glycol acrylate, polyethylene glycol acrylate, polyethyleneglycol dimethacrylate, polypropylene glycol diacrylate; or epoxy resins,unsaturated polyester resins, polyurethane resins, polyvinyl alcoholresins, polyamide resins, polyacrylic acid type resins, polymaleic acidtype resins. Further specific examples include acrylic acid esters,acrylic acid amides, methacrylic acid esters, and methacrylic acidamides.

Examples of the polymerizable monomer include ethylene glycoldiacrylate, propylene glycol diacrylate, ethylene glycol dimethacrylate,1,4-butanediol diacrylate, N,N'-methylencbisacrylamide, methyl acrylate,methyl methacrylate, cyclohexyl acrylate, benzyl acrylate, acrylamide,methacrylamide, N-methylolacrylamide, N-diacetonacrylamide, styrene,acrylnitrile, vinyl acetal, ethylene glycol diacrylate, butylene glycoldimethacrylate, 1,4-bitanediol diacrylate, 1,6-hexanedioldimethacrylate, diethylene glycol diacrylate, and triethylene glycoldiacrylate.

In order to initiate or promote the reaction of the polymerizingcomponent, a reaction initiator may be added as desired. The reactioninitiator may preferably be a radical generator such as azo compounds,organic sulfur compounds, carbonyl compounds, and halogen compounds.Specific examples of the reaction initiator used for this purposeinclude; carbonyl compounds such as benzophenone, benzyl, benzoin ethylether, and 4-N,N-dimethylamino-4'-methoxybenzophenone; organic sulfurcompounds such as dibutyl sulfide, benzyl disulfide, and decyl phenylsulfide; peroxides such as di-tert-butyl peroxide, and benzoyl peroxide;halogen compounds such as carbon tetrachloride silver bromide, and2-naphthalenesulfonyl chloride; nitrogen compounds such asazobisisobutyronitrile, and benzenediazonium chloride.

Further, in order to produce a transfer recording layer particularlyadapted to use for formation of a latent image under the combination oflight and heat energies, the reaction initiator and the polymerizingcomponent may be selected from the respective groups so as to provide acombination having a large temperature dependency of reaction velocitywith respect to the reaction between a reaction initiator which iscaused to have an activity when provided with light energy and apolymerizing component.

A preferred example of such a combination may be obtained by using aheat-fusible urethane acrylate-type polymerizable monomer as thepolymerizing component and using 2-chloro-thioxanthone orethyl-p-dimethylaminobenzoate as the reaction initiator. In order tocontrol the transferability, an acrylic resin may be additionally usedas a binder.

The coloring component or colorant is a component to provide anoptically recognizable image and may be appropriately selected fromvarious pigments and dyes. Specific examples of the colorant include:inorganic pigments such as carbon black, lead yellow, molybdenum red,and red iron oxide; organic pigments such as Hansa Yellow, BenzidineYellow, Brilliant Carmine 6B, Lake Red C, Permanent Red F5R,Phthalocyanine Blue, Victoria Blue Lake, and Fast Sky Blue; leuco dyes,and phthalocyanine dyes.

In addition, the transfer recording layer may also contain a stabilizersuch as hydroquinone, p-methoxyphenol, p-tert-butylcatechol, and2,2'-methylene-bis(4-ethyl-6-tert-butylphenol).

In order to enhance the activation of the reaction initiator, thetransfer recording layer may further contain a sensitizer such asp-nitroaniline, 1,2-benzanthraquinone, p,p'-dimethylaminobenzophenol,anthraquinone, 2,6-dinitroaniline, and Michler's ketone.

The transfer recording layer of the transfer recording medium accordingto the present invention may further contain a binder component such asa resin, wax or a mesomorphic compound.

The binder component may be resins such as homopolymers or copolymers ofpolyester type, polyamide-type, polyurethane-type, polyurea-type,polyvinyl-type, silicone-type, polyacetylene-type, and polyether-type;waxes including vegetable waxes such as candelilla wax, and carnaubawax, animal waxes such as beeswax, and whale wax, mineral waxes such asceresine wax, and montan wax, petroleum wax such as paraffin wax; andsynthetic waxes including polyethylene wax, sasol wax, montan waxderivatives, paraffin wax derivatives, hardened castor oil, hardenedcastor oil derivative, fatty acids such as stearic acid, fatty acidamides, fatty acid esters; or mesomorphic compounds such cholesterolhexanoate, cholesterol decanoate, cholesterol methylcarbonate,4'-methoxybenzylidene-4-acetoxyaniline,4'-methoxybenzylidene-4-methylaniline,4'-ethoxybenzylidene-4-cyanoaniline,N,N'-bisbenzylidene-3,3'-dimethoxybenzidine.

When the image forming elements constituting the transfer recordinglayer are provided in the form of microcapsules, the core of thecapsules may be formed of the above mentioned materials for the transferrecording layer. On the other hand, the wall of the microcapsules mayfor example be formed of a material including gelatine, gum arabic,cellulosic resins such as ethyl cellulose, and nitrocellulose, polymerssuch as urea-formaldehyde resin, polyamides, polyesters, polyurethane,polycarbonate, maleic anhydride copolymers, polyvinylidene chloride,polyvinyl chloride, polyethylene, polystyrene, and polyethyleneterephthalate.

In order to constitute the transfer recording medium according to thepresent invention into one adapted for use in multi-color imageformation, the image forming elements containing different colorants maypreferably have sensitivities to different wavelengths. As describedhereinbefore, when the transfer recording layer is composed of a number(n) of colors of image forming elements, the image forming elementsshould preferably contain n types of functional components allotted torespective colors and each providing an abruptly changing reactionvelocity when irradiated with a particular wavelength of light. Thesefunctional components in combination of n kinds are respectivelycontained in the image forming elements which are distributed to form atransfer recording layer. Examples of such a combination include, as acombination for a two-color recording system, one comprising:

a sensitizer sensitive to about 400-500 nm, such as: ##STR1##

a sensitizer sensitive to about 480-600 nm such as ##STR2##

In this case, the sensitivity regions of the above two types ofsensitizers overlap each other in the region of 480-500 nm, but this isa low sensitivity region to both types of sensitizers. Thus, they can bealmost completely separated from each other, if necessary, by usingappropriate light sources.

Sensitivity separation adapted for three color image forming elementsystem may be provided by using an azo compound having a sensitivity to340-400 nm or a halogen compound having a sensitivity to 300-400 nm incombination with the above sensitizers, so that a full-color recordingsystem may be developed.

Further, as a combination of reaction initiators, one of a2-chlorothioxanthone/ethyl p-dimethylaminobenzoate, and bdichlorobenzophenone/ethyl p-dimethylaminobenzoate, may also be used.Light sources of α a fluorescent light having a peak wavelength of 390nm and a fluorescent light having a peak wavelength of 313 nm may beused in combination with the above combination of the reactioninitiators. In order to provide the same degree of reaction (i.e., thesame transfer density level), the required illumination energy level isassumed to be 1 (standard) for a combination a - α, 4 (times) for a - β,1.1 for b - β, and 5 for b - α. As a result, if the light source α isused at the illumination energy level of 1 and the light source β isused at the illumination energy level of 1.1, the reaction initiatorsystems ○a and ○b can be separately activated so as to providesubstantially the same reaction degree.

Further, even in a case where the functional components contained in theimage forming elements have substantially the same spectral sensitivityor wavelength dependency, the respective image forming elements can havedifferent spectral sensitivities due to different filter effects ofcolorants contained therein. For example, a blue colorant transmits andreflects wavelengths of about 400-500 nm for blue light and absorbs theregion of 500-700 nm for green to red light. Accordingly, an imageforming element containing a blue colorant has a sensitivity to bluelight. For the same reason, an image forming element containing a redcolorant has a sensitivity to red light. Thus, even if image formingelements contain a functional component sensitive to a blue-red spectralrange, they can have separate sensitivities because of the colorantscontained therein.

In the transfer recording medium used in the present invention, it ispossible that the radical reactivity of the transfer recording layer issuppressed because of oxygen in the air. In order to obviate thisdifficulty, it is preferred to provide an oxygenshielding layer byapplying an aqueous polyvinyl alcohol solution containing a small amountof a surfactant on the transfer recording layer. The oxygen-shieldinglayer may be removed after the latent image formation by washing withwater. In case of image forming elements in the form of microcapsules,it is possible to have the walls show a function of the oxygen-shieldinglayer.

The color transfer recording medium used in the present invention mayfor example be produced in the following manner

The various components forming the transfer recording layer such as thefunctional component, reaction initiator, sensitizer, stabilizer,colorant, etc., may be melt-mixed and coated on a substrate such as apolyimide film by means of an application, etc., to form a transferrecording medium. In case where the transfer recording layer is formedof image forming elements of multi-colors, for example, the abovecomponents may be mixed and formed into minute image forming elements byspray drying, etc., for respective colors, and the resultant imageforming elements of respective colors are sufficiently mixed with abinder such as a polyester resin in a solvent such as methyl ethylketone and ethylene glycol diacetate and coated by a solvent-coatingmethod onto a substrate such as a polyimide film, followed by drying.e.g., at 80° C. for 3 minutes to remove the solvent to form a transferrecording layer in a thickness of 1-20 microns, preferably 3-10 microns.Thus, a desired transfer recording medium may be obtained.

In a case where the image forming elements are in the form ofmicrocapsules, they are produced in a manner, e.g., as described inExamples appearing hereinafter and may be coated on a substrate by acoating method as described above with reference to the minute imageforming elements, and using a solution of a binder such as polyvinylalcohol and an epoxy adhesive as a dispersion medium thereby to form atransfer recording layer in a thickness of 1-20 microns, preferably 3-10microns. The image forming elements, preferably in the form ofmicrocapsules, are generally formed into an average particle size of1-20 microns, preferably 3-10 microns, with a wall thickness in therange of 0.1-2 microns, preferably 0.1-0.5 micron. Substantially all theimage forming elements should preferably have particle sizes in therange of ±50%, particularly ±20% from the average particle size. Thebinder for use in microcapsule coating is, e.g., in such as amount thatit provides a thickness of 0.1-1 micron.

In the above described examples, a portion of the transfer recordinglayer provided with plural kinds of energies is caused to have anelevated melting temperature. However, if a transfer recording mediumhaving a transfer recording layer which contains a functional componentor a depolymerizing component caused to have a lower softening ormelting point, a portion of the transfer recording layer provided withplural kinds of energy directly forms a latent image to be transferred.

Examples of this type of functional components include: polymethyl vinylketone, polyvinyl phenyl ketone, copolymers of methyl vinyl ketone ormethyl isopropenyl ketone with ethylene, styrene, etc., copolymer ofvinyl chloride, acrylates, etc., with carbon monoxide, polyamide-imide,polyamide, and polysulfone.

The substrate to be used in the transfer recording medium according tothe present invention is not particularly limited, but may be knownmaterial such as polyester, polycarbonate, triacetylcellulose, nylon,and polyimide in the form of, e.g., a film or sheet.

The transfer recording layer may preferably comprise 0.1 to 10% of acolorant, 20-95% of a functional component, 0.001-20% (based on therecording layer) of a reaction initiator (when contained in thefunctional component), and 0-80% of a binder.

In the image forming method according to the present invention, pluralkinds of energies are applied to the transfer recording layer. In thefollowing, there are summarized several modes of energy application toform a latent image to be transferred.

(1) Light and heat energies are imparted to the transfer recordinglayer, under such a condition that at least one of the light and heatenergies corresponds to or is modulated by a recording informationsignal, thereby to form a latent image portion having a physicalproperty such as a melting temperature, etc., which has changed from theenergy application

(2) A reaction initiator and a polymerizing component is disposed in thetransfer recording layer in such an arrangement that they are mixed eachother at a portion applied with a pressure (e.g., the reaction initiatoris contained in capsules, which are ruptured under pressure to causemixing between the reaction initiator and the polymerizing component),and the reaction initiator is activated only on heating. Pressure andheat energies are applied to the transfer recording layer with at leastone of the energies corresponding to a recording information signal,thereby to form a latent image portion having a varied physicalproperty.

(3) A reaction initiator activatable on light exposure alone and apolymerizing component are disposed in the transfer recording layer soas to be mixed with each other under application of a pressure. Pressureand light energies are applied to the transfer recording layer with atleast one of the energies corresponding to a recording informationsignal, thereby to form a latent image portion having a varied physicalproperty.

(4) A reaction initiator activatable on application of both heat andlight energies and a polymerizing component are disposed in the transferrecording layer so as to be mixed with each other under application of apressure. Pressure, heat and light energies are applied to the transferrecording layer with at least one of the energies corresponding to arecording information signal, thereby to form a latent image portionhaving a varied physical property.

The respective energies are generally provided in such amounts that theyin combination provide a sufficient degree of change in transfercharacteristic of the transfer recording layer, and more specifically,according to the following standards:

Heat: a level sufficient to provide a temperature of 30-180° C.,preferably 70-120° C.;

Light: 10 μJ/cm² -10 mJ/cm², preferably 20-200 μJ cm² at wavelengths of250-600 nm, preforably 300-500 nm; and

Pressure: e.g., a level sufficient to cause a rupture of microcapsules;generally 5-100 kg/cm², preferably 20-50 kg/cm².

Now, several system arrangements for practicing the image forming methodaccording to the present invention will be explained with reference toFIGS. 3-8.

FIGS. 3-8 respectively show an apparatus whereby a latent image isformed in a transfer recording layer of a transfer recording medium andis transferred to a medium to be transfer-printed. Each apparatuscomprises heating means, illumination (light exposure) means, andtransfer means for transferring a latent image formed in a transferrecording layer to a medium to be transfer-printed At least one of theheating means and illumination means is driven in response to imagesignals.

FIG. 3 is a schematic side view showing an apparatus for practicing theimage forming method according to the present invention. Morespecifically, the apparatus shown in FIG. 3 is used for practicing amethod wherein a plurality of heating elements in a single heating meansare driven selectively and in response to image signals and differentlight beams respectively corresponding to colors of an image or elementsof an image to be recorded are applied to at least the portions of thetransfer recording layer heated by the driven heating elements to form amulticolor latent image to be transferred. Referring to FIG. 3, atransfer recording medium 1 according to the present invention comprisesa film substrate 1b and a transfer recording layer 1a formed thereon,the melting temperature or softening temperature of which increases whenilluminated with light under the state where it is melted or softened.The transfer recording medium 1 is wound about a feed roller 2. Anillumination means 3 disposed to illuminate the transfer recordingmedium 1 with light may be a low-pressure mercury lamp, a high-pressuremercury lamp, a metal halide lamp, a fluorescent lamp, a Xenon lamp,etc. Opposite to the illumination means 3 with respect to the transfermedium 1 is disposed a heating means 4 such as a thermal head which iscontrolled by a control circuit 5 to generate heat pulses. Instead of anordinary thermal head, a current-conduction type self-heat generativetransfer recording medium which generates heat due to a current passingtherethrough may also be used. In this case, the heating means 4 iscomposed as a current head which generates electric pulses passingthrough the medium. The heating means 4 is provided with a plurality ofheating elements (equal to resistance heating elements 20a, 20b, . . .shown in FIGS. 2A, 2B, . . . when the heating means is a thermal head,and unit electrodes when the heating means is a current head). Theheating elements may be arranged in a single row, in matrix or in aplurality of rows. Further, the heat elements may respectively bediscrete ones, or may be parts of a continuous bar-shaped resistanceheating member provided with discrete electrodes.

The apparatus further includes transfer means comprising a heat roller 8provided with a heater 7 inside thereof and a pinch roller 9 disposedopposite to the heat roller 8 so as to pinch a laminate of the transferrecording medium 1 and a medium to be transfer-printed 10 such as plainpaper or an OHP sheet (overhead projection transparency), and a winduproller 10 about which the transfer medium 1 after the transfer operationis wound up. The recorded image 12 corresponding to the latent image istransferred from the transfer medium 1 and formed on the medium 10.

The transfer medium 1 sent from the supply roller 2 is applied with heatpulses by the thermal head 4 based on image signals supplied to thecontrol circuit 5. Simultaneously with the application of heat pulses tothe transfer medium 1, different wavelengths of light are successivelyissued from the lamp 3 in synchronism with the heat pulses based on the(color) image signals. The principle of latent image formation is thesame as explained with reference to FIGS. 2A to 2D. The lamp 3 in thefigure is schematically depicted and may be composed of a plurality oflamps issuing different wavelengths of light. More specifically, if onespectral region of light is supplied from one lamp, lamps are requiredin a number equal to that of the colors of the image forming elements.

A latent image portion is formed in the transfer recording layer 1a bymeans of the thermal head 4 and the lamp 3 and is transferred to themedium to be transfer-printed 10 when passed through the heat roller 8and the pinch roller 9.

In this case, basically a single selective heating means such as athermal head is controlled based on image signals, so that the controlcircuit can be made a simple one. As a result, it is easy to realize asmall-sized highly reliable apparatus and also stable image formation.

Further, it is also possible to control both the heating andillumination based on image signals. For example, this may be realizedby heat is applied in the manner as described above with reference toFIGS. 2A-2D while light is thrown upon positions corresponding to theenergized resistance heating elements. In other words, light isuniformly illuminated in the embodiment shown in FIGS. 2A-2D, whereaslight is controlled so as to be coincidently thrown upon theheat-generated parts of the thermal head in the case where both heatingand illumination are controlled. In this manner, in a case where imageforming elements having sensitivities to particular wavelengths,wavelengths of light beams are successively changed, whereas in a casewhere image forming elements having sensitivities to particulartemperatures, the image forming elements are heated to differenttemperatures depending on their colors.

The mode wherein both heating and illumination are controlled asdescribed above is advantageous in order to obtain a large contrast orchange in transfer characteristic of a latent image, whereby a sharpimage can be obtained easily. Further, even if one type of sensitivitycharacteristic or contol-lability is deteriorated, an accompanyingdeleterious effect may be half reduced, so that a reliable apparatus canbe easily obtained.

Formation of a multi-color image has been explained in the above, but amonocolor image can also be obtained by the apparatus shown in FIG. 3,if a single colorant is used in the transfer recording layer 1a. This isalso true with the apparatus which will be explained hereinafter.

According to an embodiment of the image forming apparatus of the presentinvention, the formation of a latent image can be effected in aplurality of steps. This embodiment is shown in FIG. 4. Referring toFIG. 4, the apparatus comprises a latent image formation section and atransfer means for transferring a latent image formed in the latentimage formation section. The latent image formation section comprises aplurality of latent image formation units each comprising one heatingmeans and one illumination means, and each latent image formationsection is responsible for one color of latent image. In the embodimentshown in FIG. 4, a yellow latent image is formed by a lamp 3Y as anillumination means and a thermal head 4Y as a heating means; a magentalatent image is formed by a lamp 3M and a thermal head 4M; a cyan latentimage by a lamp 3C and a thermal head 4C; and a black latent image by alamp 3K and a thermal head 4K. Thus, respective colors of latent imageformation are successively conducted to provide a multi-color latentimage which is then transferred onto a medium to be transfer-printed 10to form a multi-color image.

This embodiment involving a plurality of latent image formation steps isadvantageous in realizing a high speed apparatus. Particularly, whenheating means such as thermal heads are used corresponding to imagesignals, the heating means are subjected to high speed repetition ofheating and cooling. Now, it is assumed that a period of 4 m.sec. isrequired for one cycle of heating and cooling of a heating means. Then,in a case where a single latent image formation step is involved and 4cycles of heating and cooling are effected one for each of Y (yellow), M(magenta), C (cyan) and K (black) latent image formation steps, at leasta period of 4 m.sec×4=16 m.sec is required for scanning of one line. Onthe contrary, if 4 latent image formation steps are involved eachresponsible for formation of one of Y, M, C and K latent images, only 4m.sec is required for scanning of one line because of parallelprocessing. In this way, high speed processing is easily conducted, sothat a high speed multicolor recording apparatus can be realized.

On the other hand, the foredescribed embodiment involving a singlelatent image formation step has an advantage that a clear multi-colorimage can be obtained, because multi-colors of an image are effected ata part in principle whereby color deviation hardly occurs.

FIG. 5 shows an apparatus for practicing another embodiment of the imageforming method according to the present invention. In the embodimentshown in FIG. 5, light illumination is controlled based on imagesignals, while heat is uniformly applied. More specifically, referringto FIGS. 2A-2D, the entire thermal head 20 is energized instead ofresistance heating elements 20b, 20d, 20e and 20f, the portions of thetransfer recording layer corresponding to the resistance heating element20b, 20d, 20e, and 20f is illuminated by a light beam with a wavelengthλ(Y). Likewise, the portions corresponding to the resistance heatingelements 20a, 20e and 20f are illuminated by a light beam with awavelength λ(M). Illumination by light beams with λ(C) and λ(K) iseffected in a similar manner.

As a result, a heating means 14 is a heater for uniformly heating thetransfer recording medium which may be a heat roller like the onedenoted by reference numeral 8 or may be one obtained by a heaterelement disposed on a ceramic substrate. Of course, it is also possibleto provide the heating means 14 with a temperature sensor and afeed-back temperature control circuit for the purpose of accuratecontrol of heating temperature. On the other hand, an array of lamps 15are provided to effect light illumination based on image signals. Thetype of the lamp array 15 may be selected according to the spectralsensitivity region of the transfer recording layer 1a and may be an LEDarray, a laser array or a liquid crystal shutter array for the visiblespectral region. Further, a laser beam scanning system, may be usedinstead of a lamp array. If the transfer recording layer has asensitivity to an ultraviolet region, an ultraviolet lamp array or anoptical system for scanning ultraviolet may be used.

According to the embodiment shown in FIG. 5, a high quality of image canbe easily attained at a high speed, a light beam which is an energysource essentially excellent in response characteristic and with lowdiffusivity is controlled based on image signals.

FIG. 6 shows another embodiment of the apparatus for practicing theimage forming method according to the present invention, wherein aplurality of recording units are provided, each comprising a latentimage formation unit and a transfer means. More specifically, a heatingmeans, an illumination means and a transfer means are combined to form arecording unit, and such recording units are used in plurality. Thecombination of latent image formation and transfer is repeated in therespective recording units on a medium to be transfer-printed to form animage comprising a combination of repetitively transferred images.

Referring to FIG. 6, in a recording unit I, an image of two colors (inthis embodiment) is formed on a medium 10, and thereafter in a secondunit II, an image of different two colors is formed by transfer onto thesame medium 10 to obtain a four-color image. It is of course possible toform a single color of image in respective recording units.Alternatively, it is also possible to practice a mode wherein an imagein, e.g., three colors of Y, M and C is formed in the recording unit Iand a black image is formed in the recording unit II which may besuperposed, as desired, on the above three color image to obtain a fourfull-color image. Other modifications are also possible.

This embodiment wherein latent image formation and transfer are effectedin each of a plurality of recording units, in advantageous inrealization of a high speed system, and improved color separation.

Incidentally, in the embodiments shown in FIGS. 3-6, it is possible toeffect the heating and the illumination sequentially, one after theother. Further, the heating and the illumination can be conducted on thesame face of the transfer recording medium, or the application of theheating and the illumination may be effected on the respectively reversefaces of the transfer recording medium from those shown in the Figures.

Further, the colorant contained in the transfer recording layer or imageforming elements can be a color precursor or a developer for developingthe color precursor. In this case, the color formation may be effectedin any of the latent image formation step, the transfer step, and a stepafter the transfer step. It is also possible to provide a developer to amedium to be transfer-printed so as to cause color formation incombination with a color precursor contained in the transferred image.Examples of such color precursors include leuco dyes and diazocompounds.

On the other hand, when colorants such as pigments and dyes causing nocolor formation reaction are used, transfer recording mediums having abetter storability and excellent stability of images after recording canbe attained. Further, it is easy to obtain a high quality multi-colorimage with a good color reproducibility.

FIG. 7 shows an apparatus for practicing a process embodiment wherein alatent image is formed by using light, heat and pressure in combination.The transfer recording medium 1 has a transfer recording layer on asubstrate. The transfer recording layer comprises capsules, through therupture of which a photoreaction initiator is caused to mix with apolymerizing component, so that the transfer recording layer is causedto have an increased softening point, melting point, etc., when providedwith light and heat energies. An ultraviolet-transmissive pressingmember 13 is formed of, e.g., quartz glass and is provided for uniformlyapplying a pressure as described above to the transfer recording medium1 to rupture the capsules. The other members are similar to those shownin FIG. 3.

Incidentally, if the transfer recording medium 1 has a transferrecording layer capable of producing latent images with only heat andpressure, the light source 3 need not be driven.

FIG. 8 shows an apparatus for practicing a process embodiment wherein apreliminary step is provided before a latent image formation step. Inthe embodiment shown in FIG. 8, a pair of pressing rollers 16 by which atransfer recording medium 1 similar to the one shown in FIG. 7 isbrought into a state where it can be reactive on exposure to light andheat energies.

The present invention provides many advantages as described below. Asthe present invention uses a transfer recording medium which abruptlycauses an irreversible change in transfer characteristic when providedwith a plurality of energies, e.g., light and heat energies, improvedstability against change in environmental conditions is obtained andhighly refined images can be obtained stably, compared with conventionalmethods such as one using only heat which is susceptible toenvironmental temperature change or one using a transfer recordingmedium which causes a change in characteristic on application of onlylight energy. Further, for the same reason, the storability of thetransfer recording medium as well as that of recorded images can beimproved.

Further, as compared with a conventional method using only a single kindof energy such as heat, in which the recording speed is controlled bythe heat response characteristic of the system or in which a long periodof time is required because an amount of energy required for imageformation is provided by a single kind of energy, the method accordingto the present invention is adapted for high speed recording because aplurality of energies are used to control the transfer characteristic.

Further, as a latent image is formed by a combination of plural kinds ofheat energies, it is easy to control stepwise the stages of change intransfer characteristic for formation of a latent image so that a mediumtone recording can be realized.

Further, according to a multi-color image formation mode of the methodof the present invention, a multi-color transfer image can be easilyformed by successively irradiating different wavelengths of lightrespectively in short periods. Compared with a conventional multi-colorheat-sensitive transfer recording method wherein a transfer recordingmedium is subjected to complex movement, the multi-color image formingmethod according to the present invention does not require a complexmovement of a transfer recording medium or a medium to be printed, sothat a multi-color image can be obtained at a high speed.

The latent image formation step and the transfer step are independentfrom each other. Therefore, transfer conditions as required for stablyproviding a high quality transferred image on a medium to be printed canbe freely and independently of the conditions for latent imageformation. As a result, the medium to be printed may be not only plainpaper as a matter of course but also selected from a wide variety mediainclusive of paper having poor surface smoothness and a transparencyfilm, on which a high quality image can also be produced. Further, anexcellent fixation characteristic is also provided.

In the image forming method according to the present invention, thelatent image formation step and the transfer step are separated, and alatent image is already formed in the transfer recording layer beforethe transfer step. As a result, the transfer step is released fromrestriction of imagewise and selective provision of energy. Thus, in thetransfer step, a level of energy sufficient for providing a clearlytransferred image on a medium to be transfer-printed depending on thesurface state of the medium. The latent image formed in the transferrecording layer is not a mere reversible image such as a heat-fusionimage but an irreversible image obtained by changing a physical propertycontrolling a transfer characteristic, so that the transfer step can beeffected reliably and faithfully to the latent image by utilizing thedifference in the physical property before and after the change duringthe transfer step. When a heat fusion image is used as a latent image asin a conventional thermal transfer recording method, the heat-fusionimage is required to be retained in a complete form from the latentimage formation step to the transfer step. However, the fading of theimage is inevitable because of decrease in transferability due tocooling between the two steps and heat conduction to the peripheralportion around the heat fusion image.

In the present invention, however, a latent image is formed through anirreversible and imagewise change in a physical property controllingtransfer characteristic such as the softening point, melting point andviscosity at a same temperature of the transfer recording layer, so thatthe physical property change is reliably memorized until the transferstep. Further, unless any energy changing the physical property isprovided after the latent image formation step, lowering intransferability or fading of a latent image is not caused. For thisreason, even in a case where the surface smoothness of the medium to beprinted is low, a high quality image can be formed and transfer can beeffected without causing degradation of image quality.

According to the image forming method of the present invention, amulti-colored transfer image can be formed without requiring complexmovement of the transfer recording medium or the medium to be printed.The multi-color transfer recording medium used in the image formingmethod according to the present invention has a transfer recording layerin which different colors of image forming elements are distributed, anda latent image of desired colors may be formed by changing conditions ofproviding plural kinds of energies and transferred onto the medium to betransferprinted. Accordingly, by changing the condition of providingplural kinds of energies sequentially in short periods, a multi-colortransferred image can be obtained at a high speed without requiringcomplex movement of the transfer recording medium or the medium to beprinted and while moving the medium to be printed in a single direction.

According to the image forming method of the present invention, colordeviation does not occur in one picture element so that a very clearimage is obtained as a whole.

In the image forming method according to the present invention, theprovision of signalized energy and the provision of uniform energy isfunctionally separated, so that the conditions for energy provision aremoderated, compared with a conventional thermal transfer recordingmethod wherein the signalized energy for latent image formation is alsoused as a energy for transfer. More specifically, in the presentinvention, the amount of energy for latent image formation is only thatrequired for causing a physical property change leading to anirreversible change in transfer characteristic while the energy fortransfer can be provided by a nonsignalized uniform energy. Thus, theamount of energy for latent image formation and the amount of energy fortransfer can be determined respectively independently, so that theconditions for energy application are moderated and a high speedrecording can be easily realized.

A thermal head used in the conventional thermal transfer recordingmethod has a heat response speed of 1-5 m.sec. at the fastest. When athermal head is driven in a shorter repetition cycle, the heating andcooling cannot be effected sufficiently in the cycle to result ininsufficient heating or remaining heat due to insufficient cooling whichleads to degradation of image quality. This is one of the most seriousobstacles to realization of high speed operation. On the contrary, inthe present invention wherein plural kinds of energies are used, when athermal head and light illumination are combined, the influence ofinsufficient cooling or remaining heat of the thermal head is removed ormoderated, because the latent image formation may be proceeded only whenthe illumination is combined with the heat from the thermal head. As aresult, even a conventional thermal head may be used for a recordingoperation in a shorter cycle by that much, so that high speed recordingcan be easily realized by the present invention.

As a latent image is formed through provision of plural kinds ofenergies in the present invention, the physical property change forforming a latent image can be easily adjusted stepwise, compared with aconventional method wherein only heat energy is used for formation of alatent image. Further, as one of the plural kinds of energy, such anenergy source as light adapted for stepwise control of the intensity maybe used, it is easy to form an image with a medium tone. For example, ifthree steps of illumination intensity or time is combined with heating,four steps of gradation (3 steps+no heating) becomes possible.

While it is also desirable that such control is effected at a highspeed, the use of an energy such as light having a high response speedin combination makes possible a high-speed medium tone recording.

Futher, by using distributed image forming elements for constituting atransfer recording layer, separation of the transfer recording layer ispromoted to provide a clear transferred image.

Futher, as the energy for latent image formation is shared by pluralkinds of energies, individual energies need not be applied so much,whereby a compact apparatus can be realized.

Hereinbelow, the present invention will be described by way of examples.

EXAMPLE 1

                  TABLE 1                                                         ______________________________________                                        Item         Component         wt. %                                          ______________________________________                                        Binder       poly(4,4'-isopropylidene-                                                                       50                                                          diphenylene-1,1,3 trimethyl-                                                  3-phenylindane-5,4'-di-                                                       carboxylate: p,p'-dihydroxy-                                                  biphenyl azelate) (25:75)                                        (Polymerizing                                                                              tri(6-acryloyloxyhexyl)-1,3,5-                                                                  20                                             component)   benzenetricarboxylate                                            Polymerizable                                                                 monomer                                                                       Reaction     benzophenone + Michler's                                                                         8                                             initiator    ketone (1:6 mixture)                                             Stabilizer   hydroquinone       2                                             Colorant     carbon black      20                                             ______________________________________                                    

The components shown in Table 1 were mixed in chloroform (solvent) andapplied under a light-shielding condition onto a 6 microns thickpolyimide film by solvent coating method and dried to form a transferrecording medium according to the present invention. The transfer mediumwas wound up in a roll and set in an apparatus as shown in FIG. 3.

The thermal head 4 was one of a line type of 8 dots/mm - A4 size havinga row of resistance heating elements at its edge portion. The thermalhead 4 was disposed so as to contact the base film 4 side of thetransfer medium 1 and in such a manner that the transfer medium 1 waspressed to the heating elements due to a tension applied to the transfermedium.

Opposite to the thermal head 4 and 2 cm spaced apart from the transfermedium 1 was disposed a high pressure mercury lamp 3.

Then, the thermal head 4 was energized while being controlled based onimage signals. In this example, the parts of the transfer recordinglayer 1a provided with light and heat were caused to have an increasedtransfer initiation temperature and an increased glass transition point,whereby a negative type of recording was effected. More specifically,the thermal head 4 was controlled in such a manner that it was notenergized in response to a mark signal (black) but was energized inresponse to a non-mark signal (white) to generate heat at a currentenergy of 0.8 W/dot×2.0 m.sec. In this way, while effecting uniformillumination with a high pressure mercury lamp, the thermal head wasdriven under control based on image signals at a repetition cycle of 5m.sec/line, in phase with which the transfer recording medium wasconveyed by means of a stepping motor and a driving rubber roller.

After a latent image portion was formed in the transfer recording layer1a, plain paper having a surface smoothness in the range of 10-30seconds was superposed on the transfer recording layer and the resultantlaminate was conveyed through a heat roller 8 and a pinch roller 9. Theheat roller 8 was an aluminum roller having a 300 W-heater insidethereof and covered with a 2 mm-thick silicone rubber layer. The surfacetemperature of the heat roller 8 was controlled at 100° C. by theheater. The pinch roller 9 was one made of silicone rubber (having ahardness of 50° according to measurement by JIS rubber hardness meter)and controlled to exert a pressure of 1.1.5 kg/cm². The thus obtainedtransfer image on plain paper was clear and of a high quality with goodfixation characteristic.

EXAMPLE 2

The components shown in Table 2 below were mixed in dichloromethane(solvent) to form a solution at a concentration of about 10%. Therefore,the solution was applied by means of an applicator on a 6 microns-thickaramide film under a light shielding condition and dried to form atransfer recording layer in a thickness of 5 microns. On the transferrecording layer was further formed a 5 microns-thick oxygenshieldinglayer for preventing suppression of radical reaction of the transferrecording layer due to oxygen by applying a 10%-aqueous solution ofpolyvinyl alcohol (PVA) containing a small account (about 0.1%) of fattyacid alkylol amide (surfactant) by means of an applicator, whereby atransfer recording medium according to the present invention wasobtained.

                  TABLE 2                                                         ______________________________________                                        Item    Component                wt. %                                        ______________________________________                                        (Poly- merizing component) Poly- merizable prepolymer                                  ##STR3##                90                                           Reaction                                                                              Michler's ketone         1                                            initiator                                                                             Benzophenone             6                                            Colorant                                                                              Kayaset Blue 136         3                                            ______________________________________                                         *1 100 g of methyl methacrylate and 100 g of glycidylmethyl methacrylate      was copolymerized in 1 liter of benzene in the presence of                    N,N'-azoisobutyronitrile (initiator) at 60° C. for 30 min. The         resultant copolymer was again dissolved in 1 liter of benzene, to which 5     g of acrylic acid and 5 g of hydroquinone were added, and the mixture was     stirred at 60° C. for 2 hours to prepare a polymerizable prepolyme     shown in Table 2. The molecular structure of the prepolymer was found to      be as shown in the table through the infrared analysis.                  

The transfer medium obtained in the above manner was wound up in a rolland set in an apparatus as shown in FIG. 3. The thermal head 4 was aline type-one of 8 dots/mm - A4 size. The light source 3 was afluorescent lamp having a peak wavelength 370 nm. To the thermal head 4was applied a power of 0.06 W/dot and a pulse duration of 50 m.sec. in acycle of 400 m.sec. corresponding to image signals. The fluorescent lampwas used to effect a uniform illumination at an intensity of 15 mW/cm²and a pulse duration of 50 m.sec. in synchronism with the thermal head.

After latent image thus formed in the transfer recording layer duringthe latent image formation step, the transfer recording medium was oncetaken out of the apparatus shown in FIG. 3 and subjected to washing withwater to remove the oxygen shielding layer. Then, the transfer recordingmedium having the latent image was incorporated in the apparatus shownin FIG. 3 and conveyed to the transfer step.

In the transfer step, the pressure between the heat roller 8 and thepinch roller 9, the structures of which were the same as those used inExample 1, was set at 25 kg/cm². The surface temperature of the heatroller 8 was controlled at 130±10° C. The medium to be transfer printedused in this example had a surface smoothness in the range of 10-30 sec.

The transfer image thus obtained on the medium to be transfer printedwas clear and of a high quality.

EXAMPLE 3

A transfer recording medium according to the present invention wasprepared in the same manner as in Example 2 except that the componentsshown in Table 3 below were used instead of those shown in Table 2.

                                      TABLE 3                                     __________________________________________________________________________    Item    Compound                       wt. %                                  __________________________________________________________________________    Binder  Polymethyl methacrylate        35                                             (Elvasite 2041)                                                       (Polymerizing component) Polymerizable monomer                                         ##STR4##                      50                                     Reaction                                                                              Irgacure 907                    8                                     initiator                                                                             (mfd. by Ciba-Geigy Corp.)                                            Colorant                                                                              Diaresin Red K                  7                                             (mfd. by Mitsubishi Kasei Kogyo K.K.)                                 __________________________________________________________________________

The transfer recording medium was used in the same manner as in Example2 to produce a transferred image on plain paper having a surfacesmoothness in the range of 10-30 sec. However, to the thermal head 4 wasapplied a power of 0.05 W/dot at a cycle of 100 m.sec and a pulseduration of 35 m.sec based on image signals. Further, a fluorescent lamphaving a peak wavelength of 313 nm was used as the light source 3 anddriven for uniform illumination at a luminance of 8 mW/cm² and a pulseduration of 50 m.sec in synchronism with the thermal head 4.

EXAMPLE 4

A transfer recording medium according to the present invention wasprepared in the same manner as in Example 2 except that the componentsshown in Table 4 were used in place of those shown in Table 2 and a 5microns thick PET film was used as the substrate. Incidentally, thepolymerizable monomer shown in Table 4 had a melting temperature ofabout 60° C.

                                      TABLE 4                                     __________________________________________________________________________    Item    Component                   wt. %                                     __________________________________________________________________________    Binder  polymethyl methacrylate     25                                                (Elvasite 2041)                                                       (Polymerizing component) Polymerizable monomer                                         ##STR5##                   55                                        Reaction                                                                              3,3',4,4'-tetra(t-butylper- 10                                        initiator                                                                             oxycarbonyl)benzophenone                                                      Michler's ketone             5                                        Colorant                                                                              Diaresin Red K               5                                                (mfd. by Mitsubishi Kasei Kogyo K.K.)                                 __________________________________________________________________________

The transfer recording medium was used in the same manner as in Example2 to produce a transferred image on plain paper having a surfacesmoothness in the range of 10-30 sec. However, to the thermal head 4 wasapplied a power of 0.18 W/dot at a cycle of 5 m.sec and a pulse durationof 2 m.sec based on image signals. Further, a fluorescent lamp having apeak wavelength of 370 nm was driven for uniform illumination at aluminance of 50 mW/cm² and a pulse duration of 2/4 m.sec in synchronismwith the thermal head.

EXAMPLE 5

The components shown in Table 1 were mixed in chloroform solvent in thedark and spray dried to form image forming elements. The particle sizesof the image forming elements were almost in the range of 3-20 microns.The image forming elements were caused to adhere under a light shieldingcondition onto a PET film already coated with an adhesive of a polyesterresin at a thickness of about 1 micron.

The thus prepared transfer recording medium according to the presentinvention was used in the same manner as in Example 1 to form atransferred image on plain paper having a surface smoothness in therange of 10-30 sec.

The transfer image thus obtained on plain paper was clear and of a highquality with good fixation characteristic.

EXAMPLE 6

Microcapsules having a core ofp-phenylene-bis(α-cyanobutadienecarboxylic acid) as a reaction initiatorwere prepared in the following manner.

10 g of a mixture of p-phenylenebis(α-cyanobutadienecarboxylic acid) andparaffin oil was mixed with a cationic or nonionic surfactant having anHLB of at least 10, 1 g of gelatine, 1 g of gum arabic and 200 ml ofwater, and the mixture was further stirred by means of a homomixer.Then, an aqueous ammonia solution was added to the mixture to adjust thepH to 11, whereby a microcapsule slurry was prepared. The slurry wassubjected to solid-liquid separation by means of a Nutsche funnel, andthe solid was dried at 35° C. for 10 hours in a vacuum drier to obtainpowdery capsules with sizes in the range of 7-15 microns and an averageof 10 microns, which comprised a core of a mixture of the initiator andthe paraffin oil encapsulated with an wall of gelatine and gum arabic.

10 parts of the microcapsules, 85 parts of an unsaturated polyesterrepresented by the formula below and 5 parts of carbon black were mixedtogether in a solvent and applied onto a 6 microns-thick PET film undera light-shielding condition to form a transfer recording medium having atransfer recording layer of about 10 microns in thickness. ##STR6##

The thus prepared transfer recording medium was wound up about a rollerand set in an apparatus as shown in FIG. 7 wherein the thermal head 4was replaced by a pressure roller surfaced with silicone rubber. Thepressure between the pressure roller and a glass pressing member 13 wasset to about 4 kg/cm². An Ar laser having a wavelength of 488 nm wasused as the light source 3 and irradiated at an energy of about 5 mJ/cm²through a polygon mirror for scanning based on image signals. Thetransfer was effected by using a heat roller 8 and a pinch roller 9which were the same as those used in Example 1 and set to exert apressure of 1 kg/cm². The surface temperature of the heat roller 8 wascontrolled within the range of 100-120° C.

In this way, a clear transfer image was formed on plain paper having asurface smoothness of 10-30 sec.

EXAMPLE 7

Microcapsules containing p-phenylenebis(α-cyanobutadienecarboxylic acid)and having an average particle size of 4 microns were prepared in thesame manner as in Example 6. The microcapsules in an amount of 10 partswere mixed with 85 parts of the unsaturated polyester used in Example 6and 5 parts of carbon black in a solvent and spray-dried to obtainparticulate image forming elements having an average particle size of 10microns.

The thus obtained image forming elements were caused to adhere onto aPET film preliminarily coated with an about 1 micron-thick adhesivelayer of a polyester resin to prepare a transfer recording mediumaccording to the present invention.

The thus prepared transfer recording medium was used to form a transferimage on plain paper having a surface smoothness of 10-30 sec., wherebya clear image was produced on the plain paper.

EXAMPLE 8

Microcapsules were prepared in the same manner as in Example 6 exceptthat p-phenylenebis(α-cyanobutadienecarboxylic acid) was replaced bymethyl ethyl ketone peroxide. The microcapsules in an amount of 10 partswere mixed with 85 parts of the unsaturated polyester and 5 parts ofcarbon black in an solvent, and the mixture was applied onto a 3.5microns-thick polyimide film under a light-shielding condition toproduced transfer recording medium according to the present inventionhaving an about 10 microns-thick transfer recording layer.

The thus prepared transfer recording medium was wound up about a rollerand set in an apparatus as shown in FIG. 7 and subjected to formation ofa transfer image without operating the light source 3. The pressurebetween a glass pressing member 13 and a thermal head 4 was set to about4 kg/cm². The thermal head 4 was a line-type one of 8 dots/mm - A4 size,to which was applied a power of about 0.15 mW/dot at a cycle of 20 m.secand a pulse duration of about 3 m.sec based on image signals. The heatroller 8 was composed of an aluminum substrate coated with a 3 mm-thicksilicone rubber layer with a hardness of 45° according to a JIS hardnessmeter and had heater inside thereof. The surface temperature of the heatroller 8 was controlled at 80-100° C. The pinch roller 9 was composed ofa silicone rubber. The pressure between the heat roller 8 and the pinchroller 9 was set at 1 kg/cm².

In this way, a clear transferred image was formed on plain paper havinga surface smoothness of 10-30 sec.

EXAMPLE 9

A transfer recording medium was prepared in the same manner as inExample 7 except that methyl ethyl ketone peroxide was used in place ofp-phenylene-bis(α-cyanobutadienecarboxylic acid). By using the transferrecording medium thus prepared, a transfer image was formed on plainpaper having a surface smoothness of 10-30 sec in the same manner as inExample 8, whereby a clear image was obtained on the plain paper.

EXAMPLE 10

The components shown in Tables 5 and 6, respectively, were separatelymixed in chloroform (solvent) and spray-dried to provide two kinds ofimage forming elements of different colors respectively having particlessizes falling almost in the range of 8-12 microns.

                                      TABLE 5                                     __________________________________________________________________________    Item    Component                wt. %                                        __________________________________________________________________________    Binder  poly(4,4'-isopropylidene-                                                                              50                                                   diphenylene-1,1,3-trimethyl-                                                  3-phenylindane-5,4'-di-                                                       carboxylate:p,p'-dihydroxy-                                                   biphenyl azelate) (25:75)                                             (Polymerizing                                                                         tri(6-acryloyloxyhexyl)-1,3,5-                                                                         20                                           component)                                                                            benzenetricarboxylate                                                 Polymerizable                                                                 monomer                                                                       Reaction                                                                              ditertiarybutylperoxyiso-                                                                               6                                           initiator                                                                             phthalate                                                             Sensitizer                                                                             ##STR7##                 4                                           Colorant                                                                              Brilliant Carmine 6B     20                                           __________________________________________________________________________

                  TABLE 6                                                         ______________________________________                                        Item   Component                 wt. %                                        ______________________________________                                        Binder poly(4,4'-isopropylidenedi-                                                                             50                                                  phenylene-1,1,3-trimethyl-3-                                                  phenylindane-5,4'-dicarboxyl-                                                 ate:p,p'-dihydroxybiphenyl                                                    azelate) (25:75)                                                       (Poly- tri(6-acryloyloxyhexyl)-1,3,5-                                                                          20                                           merizing                                                                             benzenetricarboxylate                                                  com-                                                                          ponent)                                                                       Polymer-                                                                      izable                                                                        monomer                                                                       Reaction                                                                             di-tertiarybutylperoxyiso-                                                                               6                                           initiator                                                                            phthalate                                                              Sensitizer                                                                            ##STR8##                  4                                           Colorant                                                                             Phthalocyanine Green      20                                           ______________________________________                                    

The sensitizer shown in Table 5 absorbed light in the range of about350-440 nm to initiate the reaction. The sensitizer was yellowish andcaused color-mixing with Brilliant Carmine 6B as the colorant to providea color of red at the time of image formation.

The sensitizer shown in Table 6 absorbed light in the range of about500-600 nm to initiate the reaction. The sensitizer showed a tint ofmagenta and caused color mixing with Phthalocyanine Green as thecolorant to provide a color of black at the time of image formation.

The above prepared two kinds of image forming elements were uniformlydispersed in equal amounts in a binder, and the resultant mixture wasapplied on a 6 microns-thick polyimide film under a light-shieldingconditions to form a transfer recording medium according to the presentinvention. The transfer medium was wound up in a roll and set in anapparatus as shown in FIG. 3.

The thermal head 4 was a line type-one of 8 dots/mm - A4 size having aresistance heating elements at its edge portion. The light source 3included two 40 W-fluorescent lamps 3a and 3b having a spectralcharacteristic a and a spectral characteristic b, respectively, shown inFIG. 10 disposed 2 cm-spaced apart from the transfer medium. Thefluorescent lamp 3a showing a spectral characteristic curve a was afluorescent lamp for a diazo copier with a fluorescent material of(SrMg)₂ P₂ O₇ : Eu²⁺ which was optimum for the wavelength characteristicof the sensitizer but may be replaced by another fluorescent materialsuch as Sr₃ (PO₄)₂ :Eu²⁺ or Sr₂ P₂ O₇ :Eu²⁺. The fluorescent lamp 3bshowing a spectral characteristic curve b was a green-color fluorescentlamp with a fluorescent material of (La, Ce, Tb)₂ O₃.0.2SiO₂.0.9P₂ O₅which was selected because of a practical efficiency and an operationcharacteristic but may be replaced by another fluorescent material suchas MgAl₁₁ O₁₉ :CeTb, or Y₂ SiO₅ :CeTb.

The heating elements of the thermal head 4 were energized under controlby a control circuit 5 based on image signals. In this embodiment, thetransfer recording layer la had such a property that the transferinitiation temperature increased when provided with light and heatthrough increase in glass transition temperature thereof, so that anegative type of recording was effected. In this embodiment, two-colorrecording of black and red was effected. Thus, the thermal head 4 wasnot energized in response to a mark signal (black or red) but wasenergized in response to a non-mark signal (white) to generate heat at acurrent energy of 0.8 W/dot×2.0 m.sec.

FIG. 9 shows a driving timing chart for this embodiment.

First, a current was supplied for 2 m.sec not to resistance heatingelements corresponding to an image signal of "red" but to resistanceheating elements corresponding to an image signal of "white", while thefluorescent lamp 3a for diazo copier was simultaneously turned on toeffect uniform illumination. The illumination time was 4 msec countedfrom the commencement of the energization of the resistance heatingelements. After 1 m.sec from the termination of the illumination, i.e.,after 5 m.sec from the start of energization of the heating elements, acurrent was supplied for 2 m.sec not to resistance heating elementscorresponding to an image signal of "black" but to resistance heatingelements corresponding to an image signal of "white" , while thegreen-color fluorescent lamp 3b was simultaneously turned on to effectuniform illumination. The illumination time was equally 4 m.sec.

In the above described manner, the thermal head 4 was energized undercontrol based on image signals of black, red, and white, while thetransfer recording medium 1 was conveyed by the heat roller 8 and astepping motor (not shown) in synchronism with the operation in arepetition cycle of 10 m.sec/line. After a latent image was formed inthis way, a recording paper 10 which was plain paper with a surfacesmoothness of 10-30 sec was superposed onto the latent image bearingface of the transfer medium. The resultant laminate was conveyed througha heat roller 8 and a pinch roller 9. The heat roller 8 was an aluminumroller having a 300 W-heater inside thereof and covered with a 2mm-thick silicone rubber layer. The surface temperature of the heatroller 8 was controlled at 90-100° C. by the heater. The pinch roller 9was one made of silicone rubber (having a hardness of 50° according toJIS hardness meter) and controlled to exert a pressure of 1-1.5 kg/cm².The thus obtained two-color image on the plain paper was free of colordeviation, had a high degree of saturation and clearness, and was a goodquality of image with a good fixation characteristic.

EXAMPLE 11

A transfer recording medium according to the present invention wasprepared using the components shown in Tables 7 and 8 given below in thefollowing manner.

Thus, 0.55 part of particulate silica was dispersed in a mixture of 18parts of 0.1N-hydrochloric acid and 20 parts of water. Then, 40 parts ofthe thus obtained dispersion was mixed with 55 parts of a 25%-solutionof the components shown in Table 7 dissolved in methylene chloride,under stirring at room temperature by means of a homogenizer rotating at4500 r.p.m. for 15 minutes. The dispersion was further stirred for 2hours at 60° C. to form a dispersion of image forming elements.

The above operation was repeated by using the components shown in Table8 in place of those shown in Table 7.

The thus obtained two kinds of image forming elements in dispersion wererespectively formed to have a number-average particle size of 8.6microns.

The thus obtained dispersions of two kinds of image forming elementswere mixed in equal amounts, and the mixture was applied onto a PET filmby means of an applicator under a light shielding condition so as toform substantially one layer of the image forming elements, followedby,,drying and heating at 100° C. to form a transfer recording layercomposed of a melt-adhesion layer of the image forming elements onto thePET film.

Then, a PVA layer as an oxygen-shielding layer the same as that formedin Example 1 was formed in thickness of about 5 microns on the transferrecording layer to prepare a transfer recording medium according to thepresent invention.

                                      TABLE 7                                     __________________________________________________________________________    Item    Component                  wt. %                                      __________________________________________________________________________    Binder  polymethyl methacrylate    22                                                 (Elvasite 2041)                                                       (Polymerizing component) Polymerizable monomer                                         ##STR9##                  65                                         Reaction                                                                              2-chlorothioxanthon         4                                         initiator                                                                             ethyl-p-dimethylaminobenzoate                                                                             6                                         Colorant                                                                              Diaresin Red K              3                                                 (Mitsubishi Kasei Kogyo K.K.)                                         __________________________________________________________________________

                                      TABLE 8                                     __________________________________________________________________________    Item    Component                  wt. %                                      __________________________________________________________________________    Binder  Polymethylmethacrylate     22                                                 (Elvasite 2041)                                                       (Polymerizing component) Polymerizable monomer                                         ##STR10##                 65                                         Reaction                                                                              dichlorobenzophenone        4                                         initiator                                                                             ethyl-p-dimethylaminobenzoate                                                                             6                                         colorant                                                                              Diaresin Yellow H.G.        3                                         __________________________________________________________________________

The thus prepared transfer recording medium was wound up in a roll, setin an apparatus ash shown in FIG. 3, and subjected to formation of atransfer image on plain paper having a surface smoothness of 10-30 secin the same manner as in Example 2. FIG. 11 shows a driving sequenceadopted for this operation. The light source 3 included a fluorescentlamp 3c having a peak wavelength of 313 nm and a fluorescent lamp 3d.The components shown in Table 7 are polymerized when irradiated by thelight with a peak wavelength of 370 nm, and the components shown inTable 8 are polymerized when irradiated by the light with a peakwavelength of 313 nm. A power of 0.05 W/dot was supplied to the thermalhead 4 in a cycle of 70 m.sec. and at a pulse duration of 35 m.sec. Thefluorescent lamps 3c and 3d were turned on to effect uniformillumination at a pulse duration of 25 m.sec and at a luminance of 15mW/cm² and 10 mW/cm², respectively. In FIG. 11 is also shown a pulsetiming chart for a stepping motor driven for conveying the transferrecording medium.

In this way, a clear two-color image free of color deviation was formedon the plain paper.

EXAMPLE 12

The components shown in Tables 9-12 were separately mixed in a solventand spray-dried in the same manner as in Example 10 to prepare 4 kindsof image forming elements respectively having particle sizessubstantially falling in the range of 8-12 microns.

The sensitizer and/or reaction initiator contained in the compositionsshown in Table 9-12 absorbed light in the ranges of about 280-340 nm,about 340-380 nm, about 380-450 n, and about 450-600 nm, respectively,thereby to initiate the reaction. Further, the compositions shown inTables 9-12 gave the colors of black, cyan, yellow and magenta,respectively, at the time of the image formation.

                  TABLE 9                                                         ______________________________________                                        Item           Component     wt. %                                            ______________________________________                                        (Polymerizing  polyvinyl cinnamate                                                                         70                                               component)                                                                    Polymer                                                                       Sensitizer     anthraquinone 20                                               Colorant       carbon black  10                                               ______________________________________                                    

                  TABLE 10                                                        ______________________________________                                        Item         Component         wt. %                                          ______________________________________                                        Binder       poly(4,4'-isopropylidene-                                                                       50                                                          diphenylene-1,1,3 trimethyl-                                                  3-phenylindane-5,4'-di-                                                       carboxylate: p,p'-dihydroxy-                                                  biphenyl azelate) (25:75)                                        (Polymerizing                                                                              tri(6-acryloyloxyhexyl)-1,3,5-                                                                  20                                             component)   benzenetricarboxylate                                            Polymerizable                                                                 monomer                                                                       Reaction     benzophenone +    10                                             initiator    Michler's ketone                                                 Colorant     phthalocyanine blue                                                                             20                                             ______________________________________                                    

                  TABLE 11                                                        ______________________________________                                        Item         Component           wt. %                                        ______________________________________                                        Binder       poly(4,4'-isopropylidene-                                                                         50                                                        diphenylene-1,1,3-trimethyl-                                                  3-phenylindane-5,4'-dicarboxyl-                                               ate: p,p'-dihydroxybiphenyl                                                   azelate) (25:75)                                                 (Polymerizing                                                                              tri(6-acryloyloxyhexyl) 1,3,5-                                                                    20                                           component)   benzenetricarboxylate                                            Polymerizable                                                                 monomer                                                                       Reaction     benzoin             10                                           initiator                                                                     Colorant     Benzidine Yellow    20                                           ______________________________________                                    

                                      TABLE 12                                    __________________________________________________________________________    Item    Component                wt. %                                        __________________________________________________________________________    Binder  poly(4,4'-isopropylidenedi-                                                                            50                                                   phenylene-1,1,3-trimethyl-3-                                                  phenylindane-5,4'-dicarboxylate:p,p'-                                 dihydroxybiphenyl azelate) (25:75)                                            (Polymerizing                                                                         tri(6-acryloyloxyhexyl)-1,3,5-                                                                         20                                           component)                                                                            benzenetricarboxylate                                                 Polymerizable                                                                 monomer                                                                       Reaction                                                                              di-ti-butylperoxyisophthalate                                                                          10                                           initiator                                                                     Sensitizer initiator                                                                   ##STR11##               10                                           Colorant                                                                              Brilliant Carmine 6B     10                                           __________________________________________________________________________

The above prepared four kinds of image forming elements were uniformlydispersed in equal amounts in a binder, and the resultant mixture wasapplied on a 6 microns-thick polyimide film under a light shieldingcondition to form a transfer recording medium according to the presentinvention. The transfer recording medium was wound up in a roll and setin an apparatus as shown in FIG. 12.

In this embodiment, the light source included a green color fluorescentlamp 3b as used in Example 10, a fluorescent lamp for diazo copier 3a asused in Example 10, a black light 3e (mfd. by Toshiba K.K.), and ahealth ray lamp 3f (mfd. by Toshiba K.K.). In front of the fluorescentlamp 3a, a sharp-cut filter (L-318) 18 was disposed, and in front of theblack light 3e, a sharp-cut filter (1-1A) 19 was disposed, so as toprovide desired spectral characteristics adapted for respective colorsof image forming elements.

FIG. 13 shows the spectral characteristics of the respective lightsources after modification with the use of sharp-cut filters asdescribed above.

The thermal head 4 was the same as the one used in Example 10. Thetransfer recording layer of this example also had such a property thatthe transfer initiation temperature increased when provided with lightand heat through increase in glass transition temperature thereof, sothat a negative type of recording was effected.

In operation, a current was first supplied for 2 m.sec not to resistanceheating element corresponding to an image signal of "yellow" but tothose corresponding to an image signal of "white", while the fluorescentlamp for diazo sopier 3a was simultaneously turned on to effect uniformillumination. The illumination time was 4 m.sec. After 1 m.sec from thetermination of the illumination, a current was supplied for 2 m.sec notto heating elements corresponding to an image signal of "magenta" but toheating elements corresponding to an image signal of "white", while thegreen-color fluorescent lamp 3b was simultaneously turned on to effectuniform illumination. The illumination time was 4 m.sec similarly as inthe case of "yellow". In the same manner, the black light 3e wasselectively turned on for "cyan" and the health ray lamp 3f wasselectively turned on for "black", whereby a latent image was formedwith respect to all of the four colors. The lamps 3a, 3b, 3e and 3f werecontrolled by means of a lighting control circuit 17.

In the manner as described above, the thermal head 4 was energized undercontrol based on image signals of yellow, magenta, cyan, and black in arepetition cycle of 20 m.sec/line, in phase with which the transferrecording medium 1 was conveyed by a stepping motor (not shown) and theheat roller 8. After a latent image was formed in this way, a recordingpaper 10 which was plain paper with a surface smoothness of 10-30 secwas superposed onto the latent image bearing surface of the transferrecording medium. The resultant laminate was conveyed through a heatroller 8 and a pinch roller 9. The heat roller 8 and the pinch roller 9were the same as those used in Example 10 and driven in the same manner.The thus obtained full color image on the plain paper was free of colordeviation, had a high degree of saturation and clearness, and was a goodquality of image with good fixation characteristic.

EXAMPLE 13

The transfer recording medium prepared in Example 10 was wound up in aroll and set in an apparatus as shown in FIG. 14.

Thus, a heat 14 capable of uniformly heating in an A4 size was disposedto heat the transfer recording medium 1 from the substrate 16 side, andopposite to the heater 14 was disposed a two-row liquid crystal shutterarray 21 substantially in contact with the transfer recording medium 1.The aperture size of a unit shutter 21a was 0.4×0.4 mm, and the shutterswere arranged at a pitch of 0.5 mm both longitudinally and transversely.The shutter in one row A disposed on the upstream side along themovement of the transfer recording medium 1 were applied with a yellowfilter 21b (Fuji Filter SC 50) preferentially transmitting a light beamwith wavelengths of 500 nm or above, and the shutters in the other row Bwere applied with a blue filter 21b (Fuji Filter SP1) preferentiallytransmitting a light beam with wavelengths of 500 nm or below. Above theshutter array 21 was disposed a white light source 20 (2 KW xenon lamp)for uniformly illuminating the shutter arry 21. A masking member (notshown) was disposed so that the light from the white light source 21 wasnot allowed to be incident on the transfer recording medium exceptthrough the shutter array.

Based on the above arrangement, the shutter array 21 was controlled bymeans of a masking or shutter control circuit 22 based on image signalsapplied to the circuit. In this example, a black-and-red two colornegative recording was effected. Accordingly, first in the shutter arrayrow A, shutters 21a corresponding to a "red" signal were closed, whilethe other shutters were opened for 28 m.sec, followed by closing for 12m.sec. Simultaneously therewith, in the shutter array row B, shutters21a corresponding to a "black" signal according to a preceding line orcycle of image signals were closed, while the other shutters 21a wereopened for 28 m.sec, followed by closing for 12 m.sec. In this way, theshutter array 21 was driven under control based on image signals of"black" and "red" in a repetition cycle of 40 m.sec/line, in phase withwhich the transfer recording medium 1 was conveyed by a stepping motor(not shown) and the heat roller 8. After a latent image was formed inthis way, the transfer operation was conducted in the same manner as inExample 10, whereby a two-color transfer image of good quality with ahigh degree of saturation and clearness was formed on plain paperwithout color deviation and with good fixation characteristic.

EXAMPLE 14

Image forming elements were prepared by using a core material comprisingthe components shown in the following Table 13 in the manner asdescribed following the Table 13.

                  TABLE 13                                                        ______________________________________                                        Item       Component            wt. %                                         ______________________________________                                        Binder     poly(4,4'-isopropylidenedi-                                                                        50                                                       phenylene-1,1,3-trimethyl-3-                                                  phenylindane-5,4'-dicarboxyl-                                                 ate: p,p'-dihydroxybiphenyl                                                   azelate) (25:75)                                                   (Polymerizing                                                                            tri(6-acryloyloxyhexyl)-1,3,5-                                                                     20                                            component) benzenetricarboxylate                                              Polymerizable                                                                 monomer                                                                       Reaction   benzophenone + Michler's ketone                                                                     8                                            initiator  (1:6 mixture)                                                      Stabilizer hydroquinone          2                                            Colorant   carbon black         20                                            ______________________________________                                    

A mixture of the components shown in Table 13 in an amount of 10 g wasfirst mixed with paraffin oil, and then with a cationic or nonionicsurfactant having an HLB of at least 10, 1 g of gelatine, 1 g of gumarabic and 200 ml of water. The resultant mixture was further stirred bymeans of a monomizer. Then, an aqueous ammonia solution was added toadjust the pH of the mixture to 11 or above, to obtain a microcapsuleslurry. The slurry was subjected to solid-liquid separation by means ofa Nutsche funnel at 35°) C., and the solid was dried at 35° C. for 10hours in a vacuum drier to obtain image forming elements. The imageforming elements were in the form of microcapsules with sizes in therange of 7-15 microns and an average of 10 microns, which comprises acore of the components in mixture with paraffin oil and a wall materialencapsulating the core comprising gelatine and gun arabic.

The image forming elements were caused to adhere onto a PET filmpreliminarily coated with an about 1 micron-thick adhesive layer of apolyester resin to form a transfer recording layer.

The thus prepared transfer recording medium 1 was wound up about a feedroller 2 and set in an apparatus as shown in FIG. 3, thereby to form atransfer image under the same conditions as in Example 1 inclusive ofthose for latent image formation and transferring.

As a result, a clear image of a high quality and good fixationcharacteristic was obtained on plain paper.

EXAMPLE 15

Four kinds of image forming elements respectively in the form ofmicrocapsules were prepared in the same manner as in Example 14 exceptthat the compositions shown in Tables 9-12 described in Example 12 wererespectively used as a core material. Equal amounts of the thus preparedfour kinds of image forming elements each in the particle size range of8-12 microns were dispersed in a binder and applied on a 6 microns-thickpolyimide film to form a transfer recording layer.

The thus obtained transfer recording medium was wound up in a roll andset in an apparatus as shown in FIG. 12, and subjected to formation of atransfer image under the same conditions as in Example 12 inclusive ofthose for latent image formation and transferring.

As a result, a full color image of a high quality composed of fourprimary colors of black (BK), cyan (C), yellow (Y), and magenta (M) wasobtained without color deviation, with a high degree of saturation andclearness, and with a good fixation characteristic.

EXAMPLE 16

                  TABLE 14                                                        ______________________________________                                        Item      Components            wt. parts                                     ______________________________________                                        (Polymerizing components) Polymerizable polymer                                          ##STR12##            40                                            Photopoly-                                                                              benzophenone/Michler's                                                                              3.0/0.5                                       merization                                                                              ketone                                                              initiator                                                                     Color     3-diethylamino-6-methyl-                                                                             6                                            precursor 7-phenylaminofluoran                                                Binder    polybutylmethacrylate 12                                            Polymeriza-                                                                             hydroquinone          0.5                                           tion                                                                          inhibitor                                                                     ______________________________________                                    

The components shown in the above Table 14 were mixed in a solvent andapplied onto a 6 micronsthick PET film under a light shieldingcondition, followed by drying to form a 5 microns-thick transferrecording layer. Further, a 10%-aqueous solution of polyvinyl alcoholcontaining about 0.1% of a fatty acid alkylol amide surfactant wasapplied onto the transfer recording layer to form a 3 microns-thickoxygen-shielding layer.

The thus formed transfer recording medium according to the presentinvention was cut into a width of 210 mm and set in an apparatus asshown in FIG. 3. The thermal head 4 was a line type one of 8 dots/mm -A4 size. The light source 3 was a 40 W-fluorescent lamp having a peakwavelength of 370 nm.

After a latent image was formed in the transfer recording layer duringthe latent image formation step, the transfer recording medium was oncetaken out of the apparatus shown in FIG. 3 and subjected to washing withwater to remove the oxygen shielding layer. Then, the transfer recordingmedium was incorporated in the apparatus shown in FIG. 3 and conveyed tothe transfer step.

The medium to be transfer-printed 10 was one having a coating layer ofactivated clay as a developer on the side contacting the transferrecording medium 1. The surface temperature of the heat roller 8 was setat about 80° C., and the pressure between the heat roller 8 and thepinch roller 9 was set at 25 kg/cm². After passing through the rollers,there was formed a clear black image on the medium to betransfer-printed.

What is claimed is:
 1. An image forming apparatus for a method wherein atransferable portion is formed in a transfer recording layer of atransfer recording medium, transported in a predetermined direction andis then transferred to a transfer-receiving medium to form an imagethereon, said apparatus comprising:transferable portion-forming meansfor imparting heat and light energies so that at least one of the heatand light energies corresponds to an image signal, thereby forming thetransferable portion, and transfer means for transferring thetransferable portion formed in said transfer recording layer; saidtransfer means being disposed downstream of the transfer portion-formingmeans with respect to the transporting direction of the transferrecording medium.
 2. An apparatus according to claim 1, wherein saidmeans for imparting plural kinds of energies includes heating means andillumination means.
 3. An apparatus according to claim 2, wherein saidheating means and said illumination means are disposed opposite to eachother with said transfer recording layer disposed therebetween.
 4. Anapparatus according to claim 3, wherein said transfer recording mediumcomprises a substrate and said transfer recording layer disposed on thesubstrate, said illumination means is disposed on the side of saidtransfer recording layer, and said heating means is disposed on the sideof said substrate.
 5. An apparatus according to claim 2, wherein saidheating means is a selective heating means generating heat pulses.
 6. Anapparatus according to claim 2, wherein said illumination means is ameans for applying light fluxes of different wavelengths based on imagesignals.
 7. An apparatus according to claim 6, wherein said light fluxesof different wavelengths are applied in synchronism with the heat pulsesfrom said heating means.
 8. An image forming apparatus for a methodwherein a transferable portion is formed in a transfer recording layerof a transfer recording medium, transported in a predetermined directionand is then transferred to a transfer-receiving medium to form an imagethereon, said apparatus comprising:a plurality of recording units, eachunit comprising: heating means, illumination means for forming thetransferable portion in association with the heating means and transfermeans for transferring a transferable portion formed in said transferrecording layer; at least one of said heating means and saidillumination means being driven based on image signals; said transfermeans being disposed downstream of the heating means and theillumination means with respect to the transporting direction of thetransfer recording medium.
 9. An apparatus according to claim 8, whereinsaid heating means and said illumination means are disposed opposite toeach other with said transfer recording layer disposed therebetween. 10.An apparatus according to claim 9, wherein said transfer recordingmedium comprises a substrate and said transfer recording layer disposedon the substrate, said illumination means is disposed on the side ofsaid transfer recording layer, and said heating means is disposed on theside of said substrate.
 11. An apparatus according to claim 8, whereinsaid heating means is a selective heating means generating heat pulses.12. An apparatus according to claim 8, wherein said illumination meansis a means for applying light fluxes of different wavelengths based onimage signals.
 13. An apparatus according to claim 12, wherein saidlight fluxes of different wavelengths are applied in synchronism withthe heat pulses from said heating means.
 14. An image forming apparatusfor a method wherein a transferable portion is formed in a transferrecording layer of a transfer recording medium, transported in apredetermined direction and is then transferred to a transfer-receivingmedium to form an image thereon, said apparatus comprising:atransferable portion-forming section and transfer means for transferringthe transferable portion formed in the transferable portion-formingsection onto a transfer-receiving medium, said transferableportion-forming section comprising a plurality of transferableportion-forming units each comprising heating means and illuminationmeans; said transfer means being disposed downstream of the transferableportion-forming section with respect to the transporting direction ofthe transfer recording medium.
 15. An apparatus according to claim 14,wherein said heating means and said illumination means are disposedopposite to each other with said transfer recording layer disposedtherebetween.
 16. An apparatus according to claim 15, wherein saidtransfer recording medium comprises a substrate and said transferrecording layer disposed on the substrate, said illumination means isdisposed on the side of said transfer recording layer, and said heatingmeans is disposed on the side of said substrate.
 17. An apparatusaccording to claim 14, wherein said heating means is a selective heatingmeans generating heat pulses.
 18. An apparatus according to claim 14,wherein said illumination means is a means for applying light fluxes ofdifferent wavelengths based on image signals.
 19. An apparatus accordingto claim 18, wherein said light fluxes of different wavelength areapplied in synchronism with the heat pulses from said heating means.